Glossy fibres of the modacrylic type having reduced inflammability, and compositions of matter and process for producing the same

Abstract

Modacrylic fibres from acrylonitrile, vinylidene chloride, and a sulphona comonomer, having reduced inflammability and high glossiness and dye yield are prepared by wet spinnning a polybend obtained by mixing two binary copolymers, the first from acrylonitrile and the sulphonated comonomer, and the second from acrylonitrile and vinylidene chloride. As the sulphonated comonomer, a significantly homopolymerizable monomer is used, viz. a monomer which homopolymerizes with a conversion of at least 30-40% by weight, in the presence of azobisisobutyronitrile catalyst, under given standard reaction conditions. Preferred sulphonated monomers are acid or salts of the acrylamidoalkanesulphonic series. The spinning dope is a polyblend solution in an organic solvent chosen among dimethylformamide, dimethylacetamide, and dimethylsulphoxide, mixed with water.

We claim: 
     
       1. Modacrylic fibers having a limiting oxygen Index of at least 26 and high glossiness comprising a mixture of a binary copolymer A containing from 88% to 98% of monomeric units derived from acrylonitrile and from 2 to 12% of monomeric units derived from a significantly homopolymerizable sulphonic acid monomer of the formula ##STR5## and salts of said acid, wherein R 1  is hydrogen or a short chain alkyl radical and R 2 , R 3 , R 4 , R 5  and R 6  are each hydrogen or an alkyl, cycloalkyl or aryl radical, and a binary copolymer B containing from 55% to 88% of monomeric units derived from acrylonitrile and from 12% to 45% of monomeric units derived from vinylidene chloride, the fibre containing from 12% to 40% by weight of copolymer A and from 88% to 60% by weight of copolymer B. 
     
     
       2. Modacrylic fibres according to claim 1, wherein copolymer A contains from 95% to 97% of monomeric units derived from acrylonitrile and from 3% to 5% of monomeric units derived from the sulphonic comonomer, and the copolymer B contains from 65% to 73% of monomeric units derived from acrylonitrile and from 27% to 35% of monomeric units derived from vinylidene chloride, the fibre containing from 15% to 25% by weight of copolymer A and from 85% to 75% by weight of copolymer B. 
     
     
       3. Modacrylic fibres according to claim 2, comprising about 20% by weight of copolymer A, containing about 96% of monomeric units derived from acrylonitrile and about 4% of monomeric units derived from the sulphonated comonomer, and about 80% by weight of copolymer B, containing about 70% of monomeric units derived from acrylonitrile and about 30% of monomeric units derived from vinylidene chloride. 
     
     
       4. Modacrylic fibres according to claim 3, wherein the sulphonic comonomer is chosen from the group consisting of 2-acrylamido-2-methylpropanesodium sulphonate, 2-acrylamido-propanesulphonic acid, and 2-acrylamido-2-phenylethanesulphonic acid. 
     
     
       5. A polyblend for the preparation by wet spinning of the modacrylic fibres having reduced inflammability and high glossiness of claim 1, comprising a polyblend of binary copolymer A and copolymer B. 
     
     
       6. A process for the preparation of the polyblend of claim 5, comprising mixing from 12% to 40% by weight of binary copolymer A at a temperature from 40° to 50° C. with from 60% to 88% by weight of binary copolymer B. 
     
     
       7. A process according to claim 6, wherein the binary copolymers A and B are separately prepared by polymerization to form two polymer solutions and the polyblend is prepared by mixing the two solutions obtained at the end of the polymerizations in the desired ratio, and removing the unreacted volatile monomers by distillation.